Media captionNuala Kerr: "He had all the attributes of a great police officer"

The mother of a murdered County Tyrone constable has urged people to give information about his killing, and said Catholics should still join the police.

Ronan Kerr, 25, died after a device exploded under his car on Saturday.

No-one has said they planted the device outside his home in Omagh, but dissident republicans have been blamed.

Urging people to "stand up and be counted", his mother Nuala Kerr added: "We don't want to go back into the dark days again of fear and terror."

Mrs Kerr said: "It's a sad day for our community. Ronan was a valued member and he had so much to offer.

"This is at a time when we are striving for a neutral police force for the good of our country and I urge all Catholic members not to be deterred.

"We all need to stand up and be counted and to strive for equality."

'Despicable act'

Speaking from Omagh, First Minister Peter Robinson said: "I couldn't help but get the feeling that after this there was someone, either here, or across the border who was pleased with their days work," he said.

"They think they have done something that furthers their cause but if they had spoken to the people that I have spoken to, they would know that this community is solidly standing against them.

"We must give whatever support we can to the police. We are the eyes and ears of the PSNI.

Mr Robinson said he had spoken to the Kerr family on Sunday afternoon and that they were devastated at the loss of Ronan.

"There was a young girl, who's just a few weeks off her 18th birthday, a young lad who has came back from Australia to be here for Easter and for Mother's Day," he said.

Constable Kerr's identity had been withheld until his brother, Cathair, who was en route from Australia, could be informed.

Earlier on Sunday, Northern Ireland Chief Constable Matt Baggott said the attack was carried out by a "potent and dangerous minority".

Chief Constable Baggott said they needed to speak to residents in the Highfield area of Omagh, where the bomb exploded.

"We need to know what they saw and what they heard over the past few days."

Constable Kerr, who joined the police in May 2010 and had been working in the community since December, was the second policeman to be killed since the Police Service of Northern Ireland was formed out of the Royal Ulster Constabulary in 2001.